import javax.swing.tree.TreeNode;
import java.util.LinkedList;
import java.util.Queue;

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");

    }
    public boolean isCompleteTree(TreeNode root) {
        if(root==null)
            return false;
        Queue<TreeNode> list=new LinkedList<>();
        TreeNode cur=root;
        list.offer(root);
        while(!list.isEmpty()&&cur!=null){
            cur=list.poll();
            list.offer(cur.left);
            list.offer(cur.right);
        }
        for (int i = 0; i < list.size(); i++) {
            if (list.get(i)!=null){
                return false;
            }

        }
        return true;
    }
}